1. Technical Field
The present invention relates to a track type transportation system for a vehicle which runs on a predetermined track, and in particular to a track type transportation system in which the front and rear wheels of a vehicle are automatically steered by actuators, and which incorporates therein a fail-safe mechanism for preventing the vehicle from coming off from a track upon malfunctioning of an automatic steering mechanism.
2. Background Art
The applicant has already proposed a track type transportation system for a vehicle, incorporating a steering mechanism for automatically steering the front and rear wheels of the vehicle by means of actuators so as to allow the vehicle to run on a predetermined track, and a fail-safe mechanism for preventing the vehicle from coming off the track even though the automatic steering mechanism is malfunctioning (refer to Patent Document: Japanese Patent Laid-Open No. 2006-306334). Explanation will be hereinbelow made of the track type transportation system disclosed in the Patent Document 1.
Referring to FIGS. 24 and 25, a vehicle 012 in a track type transportation system 010, runs along a track 01 incorporating a U-like sectional shape protection track 014 laid substantially on its center line and formed in a channel-like configuration with respect to a road surface 015. The U-like sectional shape protection track 014 is formed of a U-like channel steel laid on the road surface.
The vehicle 012 is provided with a front wheel bogie 016 and a rear wheel bogie (which is not shown) for supporting the vehicle 012, underneath the vehicle 012 in a front and a rear part thereof. The front wheel bogie 016 is mounted thereto with an axle for front wheels 018 so as to be pivotable left and right. The front wheels 018 are mounted thereon with a core type rubber tire 020 which is although not shown. Further, the rear wheel bogie is also mounted thereto with an axle for rear wheels 022 so as to be pivotable left and right. The rear wheels 022 are also mounted thereon with rubber tires 020 which is although not shown.
Next, explanation will be made of a steering mechanism, focusing on the front wheel 018 side. It is noted that the rear wheel 018 side has also a configuration similar to that of the front wheel side.
As shown in FIGS. 24 and 25, there are provided a front steering arm 028a connected to the front left wheel 018b and extending forward, and a rear steering arm 030a extending rearward. The front right wheel 018a is provided thereto with a rear steering arm 30b extending rearward. The steering arms 030a, 030b of the front left and right wheels are mounted with a tie rod spanning between their lower end parts. These rear steering arms 030a, 030b are rotatably coupled to the tie rod 032 by means of spherical joints 034.
Further, the front end part of the front steering arm 028a is coupled rotatably thereto with a distal end part of a movable rod 038 of an actuator 036 by means of a spherical joint 034. The actuator 036 is attached to the front wheel bogie 016. As to a specific structure of the actuator 036, there is used a ball-screw structure with a motor as will be described later. However, any means capable of carrying out translational motion, such as a pneumatic or hydraulic cylinder, a linear motor or the like may be used.
It is noted that the tie rod 032 and the rear steering arms 030a, 030b constitute the so-called Ackerman-Jeantaud type link mechanism for appropriately controlling the steering angles of the left and right wheels upon turning. Further, the left wheels 18b and the right wheels 18a are linked together by the tie rod 032, and accordingly, the left and right wheels can surely be steered.
Next, explanation will be made of protection wheels 040. The protection wheels 040 are cylindrical, and are rotatably supported respectively to the front and rear end parts of a protection arm 042 on the rear surface side. Further, the protection wheels 040 are inserted in the U-like protection track 014 so that their peripheral surfaces are faced to the side walls of the protection track 014. The protection wheels are made of a material which is desirably, highly vibration-resistant and wear-resistant urethane rubber, a material utilizing a steel belt as used in a rubber type or the like.
Further, the protections wheels 040 and the side walls of the protection track 014 define therebetween gaps which are less than an allowable range the vehicle 012 should not turn further more left and right, and the protection wheels do not make contact with the sidewalls of the protection track 014 whenever the steering mechanism is normally operated. Normally, the gaps between the protection wheels and the protection track 014 are set in a range from about to 80 to 100 mm.
The protection arm 042 has a shape which is elongated in the longitudinal direction of the vehicle, and is rotatably supported in its center part to the lower part of the axle 044 of the front wheel 018.
It is noted that the height of the protection wheels 040 may be set so that they are arranged above the road surface 015 as shown in FIG. 25(a) or below the road surface 015 as shown in FIG. 25(b). Thus, any suitable structure may be selected so as to be adaptable for an existing track in view of its replace specification, that is, the adaptation is more flexible.
The protection arm 042 is coupled in the vicinity of the one end part thereof to the front end part of the front steering arm 042 through the intermediary of a link rod 046, and accordingly, the link rod 046 and the protection arm 042 cause the protection wheels 040 to be directed in the same direction as the steering direction of the front wheels 018.
The steering mechanism is composed of the actuator 036, the movable rod 038, the front steering arm 028a, the rear steering arms 030a, 030b, and the link mechanism is composed of the protection arm 042 and the link rod 046.
Further, the steering arm 028a is provided in its front end part with a double surface joint 050 with which one end part of the movable rod 038 of the actuator 036 and one end part of the link rod 046 are coupled to the front end part of the front steering arm 028a, being overlapped one upon another. With the use of the above-mentioned double spherical joint 050, it is possible to aim at effectively use a space.
The structure for mounting the steering mechanism, the protection arm 042 and the actuator 036 onto the front wheel bogie 016 will be explained with reference to FIGS. 26 and 27.
There is provided an axle housing 060 in which a differential mechanism portion 056 inputted thereto with a drive power from a drive motor (which is not shown), is integrally incorporated with an axle portion 058 for transmitting a drive power to the left and the right wheels, and a bogie frame 062 is provided above the axle housing 062.
The protection arm 042 is attached thereto with a support bracket 064 supported to the lower part of the differential mechanism portion 056, the rotating center thereof being located at the center of the axle. The support bracket 064 is attached in its upper part to the bogie frame 062, being extended downward around the differential mechanism portion 056, and has, in its lower part, a protection frame 066 for rotatably holding the protection arm 042. The protection frame 066 has a center support structure, for a pivotal fulcrum of the protection arm 042, in which the pivotal fulcrum is vertically interposed. Further, the protection frame 066 is formed with left and right vertical walls 068a, 068b which are capable of limiting the pivotable range of the protection arm 042.
As shown in FIG. 27, the actuator has such a unit structure that an electric motor 072, a clutch 074, a ball screw 076 and a limit guide 078 are assembled to the lower surface part of an L-like sectional shape frame 070. The frame 070 having such a unit structure that the above-mentioned components are assembled thereto is fastened to the bogie 062 by means of bolts. The ball screw 076 has a feed nut part 080 which is joined thereto with one end part of the movable rod 038 of the actuator 036, and the other end part of the movable rod 038 is joined to the upper spherical surface part 052 of the double spherical joint 50 so as to be coupled with the front steering arm 028a. 
Further, as shown in FIG. 26, one end part of the protection arm 042 and the lower spherical joint part 054 of the double spherical joint 050 are connected therebetween by means of the link rod 46, and are then coupled to the front steering arm 028a. The rear steering arm 030a is jointed in its rear end part with the tie rod 032, and is coupled to the rear steering arm 030b for the right wheel.
With the above-mentioned mounting structure in which the protection arm 040 mounted thereto with the protection wheels 040 is supported to the lower part of the differential mechanism portion 056 of the highly rigid axle housing 060 so as to use the support bracket 064 attached to the bogie frame 062 in order to eliminate the necessity of the modification of the bogie for attaching the protection arm 042, the existing bogie frame 062 for the front wheels can be used as it is. Thereby it is possible to aim at commonly using the components of the bogie frame 062 and at reducing the manufacturing costs. Further, since the unit structure of the actuator is mounted on the bogie frame 062, the efficiencies of the assembly work, the component replacement work and the maintenance service can be enhanced. Due to the unit structure, the configuration can be simplified, thereby it is possible to aim at allowing the apparatus to be lightweight.
Further, the actuator 036 is normally operated in response to a steering instruction from a control means which is not shown, so as to apply a steering force to the front left wheel 048b by the actuator 036, and then, the steering force is transmitted from the front steering arm 028 to the rear steering arm 030a, and is then transmitted therefrom to the front right wheel 018a through the intermediary of the tie rod 032. Further, the steering force from the actuator 036 is also transmitted from the double spherical joint 050 to the protection arm 042 through the intermediary of the link rod 046, and accordingly, the protection wheels 40 are also moved in association with the motion of the actuator 036 so as to be directed in the same direction as that of the front wheels 018. Thus, the protection wheels 040 are moved in the protection track 014 together with the wheel 012 without making contact with the side walls of the protection track 014.
Upon malfunctioning of the above-mentioned steering mechanism, the protection wheels 040 make contact with the left and right walls of the protection track 014, and accordingly, it is possible to prevent the vehicle from running away from the track.
In the steering system disclosed in the Patent Document 1, whether the vehicle follows up a desired locus or not is determined, and the front wheels and the rear wheels of the vehicle are automatically steered by the actuators so as to guide the vehicle. However, it is necessary to measure a deviated value widthwise of the track with respect to the advancing direction of the vehicle in order to precisely determine whether the vehicle follows up a desired running locus (which is precisely a line connecting the centers of the respective axles of the front and rear wheel bogies of the vehicle).
In order to measure the deviated value of the vehicle, widthwise of the track, there is required an on-ground structure serving as a reference position for the measurement. Further, a noncontact type measuring instrument which has a high degree of measuring accuracy, and which does not cause any wearing problem is preferably used as a measuring device therefor, and such a noncontact type measuring instrument would cause a risk with respect to its environmental resistance in view of rain water, sunlight or the like. Thus, there would be possibly caused a trouble throughout the entire system upon occurrence of a detection error.